1. Technical Field
The present invention relates to a position detector and a liquid ejecting apparatus incorporating the same.
2. Related Art
In an ink jet printer, a carriage and a printed subject such as paper are driven by a motor. Incidentally, in order to perform position control and speed control, an encoder is generally used. The encoder includes a photo sensor and a scale. The photo sensor includes a light emitting element and a light receiving element the scale includes a light transmitting section which transmits light emitted from the light emitting element, and a light shielding section which shields light emitted from the light emitting element. These light transmitting section and light shielding section are repetitively arranged at a fixed pitch.
In such the encoder, recently, there is a problem of attachment of ink mist. Namely, recent printers which perform printing with high precision can eject minute ink droplets from a printing head. These minute ink droplets readily become ink mist and drift inside the printer. Therefore, as such the printer is used for a while, solidified ink mist is piled on the scale.
Japanese Patent Publication No. 2005-81691A (JP-A-2005-81691) teaches that a partition member is arranged between a carriage belt and a scale to prevent the attachment of the ink mist onto the scale. Japanese Patent Publication No. 2004-202963A (JP-A-2004-202963) discloses a configuration for correcting, in a case where duty factor of a signal outputted from a light receiving element decreases due to the attached ink mist, the duty factor of the output signal so as to become 50%.
In a case where the ink mist is attached onto the light transmitting section of the scale, light which passes through the light transmitting section is diffracted and causes a disadvantageous effect. Any means for preventing such the disadvantage has not been disclosed in the above publications.